01 - Preheat your oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish. Arrange the hot dog buns in the prepared dish, fitting them snugly, and place one hot dog into each bun.
02 - Evenly distribute the canned chili over the encased hot dogs and buns, ensuring a thorough coating. Sprinkle the chopped onion and half of the shredded cheddar cheese over the chili.
03 - Drizzle the melted butter evenly across the top. If desired, for enhanced flavor, add the optional yellow mustard and ketchup.
04 - Top the casserole with the remaining shredded cheddar cheese. Cover the baking dish securely with aluminum foil and bake for 25 minutes. Following this, remove the foil and continue to bake for an additional 10 minutes, or until the cheese is fully melted and bubbling.
05 - Remove the casserole from the oven and allow it to rest for 5 minutes. Garnish with sliced green onions and pickled jalapeños, if using.
06 - Serve the chili cheese dog casserole hot.